The Sim/Tech STF-130 maintenance sleeve inserts into the outlet of the tank to block off flow, preventing built up solids and unfiltered effluent from exiting the tank when the filter is removed. This means that the septic tank owner doesn’t have to pay to have their tank pumped every time the filter is serviced (though tanks should be pumped on a regular basis for optimum performance). It also means that the system is always protected even when the filter is being serviced or inspected.